Turn Island is a 34-acre (14 ha) island in the San Juan Islands in the Salish Sea in the U.S. state of Washington. The island sits in the San Juan Channel about 900 feet off the east coast of San Juan Island. It is preserved as Turn Island Marine State Park and is part of the San Juan Islands National Wildlife Refuge. The island has 12 campsites and is only accessible by water. A few meters off the west shore of Turn Island, astride Boat Channel lies an unnamed island.